This invention relates to a method for measuring the maximum gross weight of a motor vehicle, by use of an image-processing step, in order to determine the charge for a motor vehicle using a toll road, such as a toll express highway.
Since a broad variety of motor vehicles use toll roads, motor vehicle type must therefore be taken into consideration when determining an appropriate charge for the vehicle using the toll road. In other words, the charge for the motor vehicle in question should be determined primarily in accordance with its size and especially its gross weight. Using vehicle gross weight as a factor in determining an appropriate charge is considered reasonable, in view of the possible damage the vehicle may cause to the road. Here, the term "gross weight of the vehicle" is intended to mean the weight of the vehicle per se, plus the load carried by the vehicle, and including the occupants.
Therefore, various devices have been developed for measuring the gross weight of a motor vehicle, such as those described in Japanese Patent Disclosure (KOKAI) Nos. 53-41248, 53-41249, and 61-50013. These known devices use a load sensor to measure the gross weight of the vehicle. Various such sensors are known, as are shown in these Japanese Patent Disclosures. All these sensors, however, suffer from poor durability, since they have to bear the actual weight of the vehicle, in order to measure its gross weight. Where, therefore, the actual gross weight of the vehicle is to be measured directly, it is necessary to initially perform the time-consuming checking and maintenance of the load sensor. To neglect to do so will likely result in inaccurate measurement of the gross weight of the vehicle. Furthermore, even if the gross weight of the vehicle is to be measured using the known measuring device, i.e. while the vehicle is in motion, the weight value indicated by the load sensor will vary, depending upon the speed at which the vehicle is moving. When, therefore, the gross weight of the vehicle is to be precisely measured, it must be carried out with the vehicle stopped. This inevitably makes the weighing of each individual vehicle a time-consuming process.
As must be clearly evident from the above explanation, this method of measuring the gross weight of the vehicle, to determine its road toll charge, is not a realistic approach. It is common practice, therefore, to determine the road toll charge on the basis of the maximum gross weight of the vehicle rather than to determine its actual gross weight. Here, the term "maximum gross weight" is intended to mean the weight of the vehicle per se, plus the maximum allowable load, and including the occupants. In other words, it is usual practice for the road toll charge to be determined in accordance with the maximum allowable gross weight, regardless of the actual load (including the occupants) being carried by the vehicle, as opposed to determining the actual gross weight of the vehicle.
It is therefore desirable that, in order to determine the charge for a vehicle using a toll road, the aforementioned maximum gross weight can be measured without the need to measure the actual gross weight of the vehicle.